A drone is an unmanned aerial vehicle or UAV. Many drones closely resemble airplanes and are powered like an airplane.
Drones are often used for military purposes and/or for observation operations. The drone is sent over the area to be observed, carrying with it the image capture and transmission equipment necessary to complete its mission. It is known to have drones flying above 10,000 m, for example 20,000 m, and able to remain in the air for more than 24 hours with a payload of one or more metric tons.
Another application of a HALE drone is, for example, to serve as a stratospheric platform. A machine is placed at high altitude in the stratosphere (between about 12 and 50 km in altitude) and remains stationary relative to the ground, similarly to a geostationary satellite but at a much lower altitude. Such a drone can preferably remain in position for several weeks or months. It then serves as a telecommunications relay for example, for telephony and/or for images (television) from terrestrial observation for civilian or military purposes, etc.
Projects of this type exist, but no proposed solution allows maintaining a payload of several hundred kilograms or several metric tons in position above a target for several days.